rustdoc: Only analyze head of self type when deciding impl inlining by camelid · Pull Request #159854 · rust-lang/rust

camelid · 2026-07-24T17:05:39Z

We only care about whether the self type is a generic or an item (inlined) in
the current crate, so we don't actually need to compute the param_env, which is
expensive when done to every external impl. This PR avoids computing the
param_env until we actually decide to inline the impl. Moreover, it adds
specialized cleaning logic for types that stops after the "head" (the top-level
structure) is constructed, which is enough for the self type-based impl
inlining analysis.

camelid · 2026-07-24T17:05:46Z

@bors try @rust-timer queue

rustdoc: Only analyze head of self type when deciding impl inlining

rust-bors · 2026-07-24T19:11:56Z

☀️ Try build successful (CI)
Build commit: b8110ca (b8110ca9b8652ec8b2b3ae78916c0f05ed62d565)
Base parent: 29e68fe (29e68fe2295f8fc2feb52b8cb0b61a055842fdcf)

rust-timer · 2026-07-24T19:53:53Z

Finished benchmarking commit (b8110ca): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

@bors rollup=never rustc-perf
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-8.4%	[-37.1%, -0.8%]	19
Improvements ✅ (secondary)	-21.1%	[-36.9%, -2.4%]	24
All ❌✅ (primary)	-8.4%	[-37.1%, -0.8%]	19

Max RSS (memory usage)

Results (primary -5.9%, secondary -8.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	3.1%	[3.1%, 3.1%]	1
Regressions ❌ (secondary)	6.0%	[6.0%, 6.0%]	1
Improvements ✅ (primary)	-6.4%	[-11.8%, -1.2%]	20
Improvements ✅ (secondary)	-9.3%	[-12.7%, -2.9%]	23
All ❌✅ (primary)	-5.9%	[-11.8%, 3.1%]	21

Cycles

Results (primary -11.5%, secondary -23.6%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.5%	[2.5%, 2.5%]	1
Improvements ✅ (primary)	-11.5%	[-38.4%, -2.6%]	17
Improvements ✅ (secondary)	-24.7%	[-38.6%, -2.7%]	23
All ❌✅ (primary)	-11.5%	[-38.4%, -2.6%]	17

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 488.104s -> 487.819s (-0.06%)
Artifact size: 387.69 MiB -> 387.70 MiB (0.00%)

We only care about whether the self type is a generic or an item (inlined) in the current crate, so we don't actually need to compute the param_env, which is expensive when done to every external impl.

rustbot · 2026-07-24T20:10:42Z

r? @notriddle

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rustdoc expanded to 8 candidates
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camelid · 2026-07-28T17:00:28Z

Ugh, we really should enable compiler-docs in CI to avoid these annoying last-minute failures. Maybe we can enable mergeable CCI for internal docs since that should provide a big speedup to rustdoc?

With -Zrustdoc-mergeable-info, building compiler-docs goes from ~1m7s to ~20-25s on my desktop (on this branch, with all the rustdoc perf fixes I've done).

rustdoc: Only analyze head of self type when deciding impl inlining We only care about whether the self type is a generic or an item (inlined) in the current crate, so we don't actually need to compute the param_env, which is expensive when done to every external impl. This PR avoids computing the param_env until we actually decide to inline the impl. Moreover, it adds specialized cleaning logic for types that stops after the "head" (the top-level structure) is constructed, which is enough for the self type-based impl inlining analysis.

Kobzol · 2026-07-28T17:31:30Z

Ugh, we really should enable compiler-docs in CI to avoid these annoying last-minute failures. Maybe we can enable mergeable CCI for internal docs since that should provide a big speedup to rustdoc?

With -Zrustdoc-mergeable-info, building compiler-docs goes from ~1m7s to ~20-25s on my desktop (on this branch, with all the rustdoc perf fixes I've done).

If it doesn't have any trade-offs that we would care about, please do send a PR! Building docs is indeed a non-trivial bottleneck for our CI.

This feature is unstable but will be stabilized soon, and this is a good way of dogfooding it to make sure it works properly. It should have no effect on the generated docs, but it provides a significant speedup. For example, I measure a 3x speedup locally (3m 11s -> 1m 1s) -- note that this is with the latest rustdoc perf improvements (#159854).

rust-log-analyzer · 2026-07-28T19:12:33Z

The job dist-x86_64-solaris failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

rust-bors · 2026-07-28T19:13:37Z

💔 Test for e59475a failed: CI. Failed job:

auto - dist-x86_64-solaris (web logs, enhanced plaintext logs)

camelid · 2026-07-28T19:14:51Z

Argh. Appears spurious AFAICT. I don't even see an error in the logs, weirdly...

@bors retry spurious>

JonathanBrouwer · 2026-07-28T19:30:10Z

Just to be sure
@bors try jobs=dist-x86_64-solaris

rustdoc: Only analyze head of self type when deciding impl inlining try-job: dist-x86_64-solaris

rust-bors · 2026-07-28T21:20:34Z

☀️ Try build successful (CI)
Build commit: 217458e (217458eabef1c6d9349658606aaa4460fcb75fb7)
Base parent: e19d321 (e19d321c06479c6fd77533582b0d5a86651f1be3)

rust-bors · 2026-07-29T02:23:27Z

☀️ Test successful - CI
Approved by: notriddle,GuillaumeGomez
Duration: 3h 42m 18s
Pushing 701a651 to main...

github-actions · 2026-07-29T02:26:12Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 26ae60a (parent) -> 701a651 (this PR)

Test differences

Show 6 test diffs

Stage 1

[rustdoc-html] tests/rustdoc-html/inline_cross/impl-for-projection-reexport.rs: [missing] -> pass (J0)

Stage 2

[rustdoc-html] tests/rustdoc-html/inline_cross/impl-for-projection-reexport.rs: [missing] -> pass (J1)

Additionally, 4 doctest diffs were found. These are ignored, as they are noisy.

Job group index

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 701a6513a48eac30d49110ba06187648b7553622 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

x86_64-gnu-gcc-core-tests: 14m 41s -> 8m 45s (-40.3%)
x86_64-gnu-llvm-21-1: 54m 59s -> 34m 57s (-36.4%)
dist-powerpc64le-linux-musl: 1h 12m -> 1h 36m (+33.7%)
x86_64-msvc-ext2: 2h 2m -> 1h 23m (-31.6%)
i686-msvc-1: 2h 13m -> 2h 54m (+30.0%)
x86_64-gnu-llvm-21-3: 1h 46m -> 1h 17m (-27.6%)
x86_64-gnu-miri: 1h 39m -> 1h 14m (-25.1%)
x86_64-gnu-gcc: 1h 14m -> 56m 24s (-24.8%)
x86_64-msvc-1: 1h 59m -> 2h 27m (+23.3%)
x86_64-msvc-ext1: 2h 7m -> 1h 38m (-23.3%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2026-07-29T03:04:49Z

Finished benchmarking commit (701a651): comparison URL.

Overall result: ✅ improvements - no action needed

@rustbot label: -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-9.1%	[-39.9%, -0.9%]	19
Improvements ✅ (secondary)	-22.8%	[-39.7%, -2.6%]	24
All ❌✅ (primary)	-9.1%	[-39.9%, -0.9%]	19

Max RSS (memory usage)

Results (primary -6.5%, secondary -10.6%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	2.8%	[2.8%, 2.8%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-7.0%	[-13.7%, -1.5%]	20
Improvements ✅ (secondary)	-10.6%	[-13.2%, -3.0%]	23
All ❌✅ (primary)	-6.5%	[-13.7%, 2.8%]	21

Cycles

Results (primary -12.1%, secondary -25.4%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.0%	[2.8%, 3.3%]	2
Improvements ✅ (primary)	-12.1%	[-41.4%, -3.0%]	19
Improvements ✅ (secondary)	-27.8%	[-41.8%, -4.4%]	23
All ❌✅ (primary)	-12.1%	[-41.4%, -3.0%]	19

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 489.651s -> 491.747s (0.43%)
Artifact size: 390.13 MiB -> 390.11 MiB (-0.00%)

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-rustdoc Relevant to the rustdoc team, which will review and decide on the PR/issue. labels Jul 24, 2026

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rust-bors Bot pushed a commit that referenced this pull request Jul 24, 2026

Auto merge of #159854 - camelid:selfty-head, r=<try>

b8110ca

rustdoc: Only analyze head of self type when deciding impl inlining

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 24, 2026

camelid commented Jul 24, 2026

View reviewed changes

Comment thread src/librustdoc/passes/collect_trait_impls.rs Outdated

rustdoc: Skip param_env when making impl inlining decisions

f5b3643

We only care about whether the self type is a generic or an item (inlined) in the current crate, so we don't actually need to compute the param_env, which is expensive when done to every external impl.

camelid force-pushed the selfty-head branch from 5377944 to 74939c0 Compare July 24, 2026 20:10

camelid marked this pull request as ready for review July 24, 2026 20:10

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 24, 2026

rustbot assigned notriddle Jul 24, 2026

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Jul 24, 2026

camelid force-pushed the selfty-head branch from 74939c0 to 0b267ab Compare July 24, 2026 20:30

GuillaumeGomez reviewed Jul 24, 2026

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Comment thread src/librustdoc/passes/collect_trait_impls.rs Outdated

camelid force-pushed the selfty-head branch 3 times, most recently from 69b025c to a1136eb Compare July 25, 2026 18:04

notriddle requested changes Jul 26, 2026

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Comment thread src/librustdoc/passes/collect_trait_impls.rs

Comment thread src/librustdoc/passes/collect_trait_impls.rs Outdated

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 26, 2026

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rustbot added the T-rustdoc-frontend Relevant to the rustdoc-frontend team, which will review and decide on the web UI/UX output. label Jul 27, 2026

rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 28, 2026

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camelid mentioned this pull request Jul 28, 2026

bootstrap: Enable rustdoc mergeable CCI for std and internal docs #160098

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rust-bors Bot pushed a commit that referenced this pull request Jul 28, 2026

Auto merge of #159854 - camelid:selfty-head, r=<try>

217458e

rustdoc: Only analyze head of self type when deciding impl inlining try-job: dist-x86_64-solaris

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rust-bors Bot added merged-by-bors This PR was explicitly merged by bors. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jul 29, 2026

rust-bors Bot merged commit 701a651 into rust-lang:main Jul 29, 2026
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rustbot added this to the 1.99.0 milestone Jul 29, 2026

camelid deleted the selfty-head branch July 29, 2026 15:36

camelid mentioned this pull request Jul 30, 2026

Tracking issue for release notes of #159623: rustdoc: Only build extern trait impls if needed #159674

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notriddle mentioned this pull request Aug 25, 2026

bootstrap: Enable rustdoc mergeable CCI for std and internal docs #161716

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Overall result: ✅ improvements - no action needed

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Test differences

Stage 1

Stage 2

Job duration changes

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Overall result: ✅ improvements - no action needed

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